Geological mapping and geophysical surveying on the earth's surface are mature sciences with a history of technology enhancements that improved the fidelity of understanding of the Earth, above and beneath the surface. Yet when conventional techniques are employed in an underground environment, geo-location has proven a challenge that drives concepts of operations to bootstrap techniques to geo-locate instrumentation and geological contacts and can actually limit the effectiveness of employed technologies.
Conventional mapping and survey systems, such as a Global Positioning System (GPS), determine the location of objects using satellite signals. However, a longstanding problem exists with determining location of personnel and equipment within, for example, underground facilities without the use of surveying. To date, this problem has not been resolved because of the difficulty of signaling/communicating between the Earth's surface and underground facilities/caverns/mines and the complexity of electromagnetic propagation within the Earth.
Lower fidelity very low frequency systems are currently in development in Europe to support communications for cave rescue operations. The systems only obtain a shallow depth position when the communication system is used underground. These communications systems are effective up to 600 m and occasionally to 1,200 m. The systems are also used to locate underground transmitters at comparable depths. In controlled experiments, they have achieved an accuracy of 2% in horizontal position and only 5% in depth.